In virtual desktop infrastructures (VDIs), virtual desktop operating systems and applications, hosted on virtual machines (VMs) running on centralized servers, are delivered as managed services to end users via a network. Such centralized and automated management of the virtualized operating system, applications, and user data provides increased control and cost savings.
In a VDI environment, a framework may be applied to measure system performance. One measurement of system performance is a user experience test. A user experience test measures the speed, smoothness (evenness), and responsiveness when a window is dragged across a screen on a remote desktop or when content is scrolled inside a window. The user experience test tracks the movement of a particular bitmap painted inside the window that is being dragged or scrolled. The bitmap is designed so that reading the color of a pixel and its neighbors uniquely identifies the location of that pixel inside the window or within the content being scrolled. Using that information, the position of the entire window or content can be computed.
This approach has several drawbacks. First, the bitmap that is used is often color rich, more so than most other content that is used by a typical user. Measuring window-drag performance using a color-rich bitmap may result in performance measures that differ significantly from what an ordinary user actually experiences.
Second, since the bitmap assigns a unique color value to each pixel, any change in the color value due to lossy compression might cause the pixel to be misidentified or not identified at all by the client VM. Identification errors make it difficult to reliably measure the position of the window.
Third, since the color changes from one pixel to the next in the bitmap, high frequency components may be introduced in the signal that could change the behavior of the compression algorithm. Therefore, the performance measurement technique could significantly impact the performance that is being measured.